Electric immersion heater



1956 J. w. HARRISON ELECTRIC IMMERSION HEATER Filed Jan. 10, 1955 I NVENTOR J OH N W. HARR ISON FIGZ.

ATTORN EY United States Patent ELECTRIC IMMERSION HEATER John W. Harrison, Meadville, Pa., assignor to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Application January 10, 1955, Serial No. 480,641

4 Claims. (Cl. 219-38) This invention relates to a sheathed electrical immersion heating device for mounting in the wall of a liquid containing receptacle.

It is an object of this invention to simplify the construction of a hermetic seal about the heater terminals in a heater of the above type.

It is another object of this invention to provide an improved sturdy construction, for mounting and for making electrical connections, in a heater of the above mentioned type in which a molten hermetic sealing material may be poured and formed about the heater terminals without requiring the use of auxiliary molding apparatus.

In accordance with this invention a sheathed heater is bent with its sheathed end portions parallel and adjacent to each other. The terminal ends of the heater extend through a corrosion resistant sheet. A clamping plate having a central opening therein abuts the sheet to reinforce it. Abutting the outer side of the clamping plate is an insulating terminal block having a recess therein aligned with the opening in the plate. The opening in the plate and the recess in the block define a cavity into which the terminal portions of the heater extend and within which the heater sheath terminates. The heater terminals extend to the outside of the block for making electrical connections thereto. The cavity is accessible by means of a passage in the block through which molten sealing material is poured to form an electrically insulating hermetic seal between the sheath and the heater terminals. After pouring the sealing material into the cavity an insulating plug may be inserted to close the passage.

These and other objects are effected by the invention as will be apparent from the following description taken in connection with the accompanying drawings, forming a part of this application, in which: 7

Fig. 1 is a vertical section taken along the line I-I of Fig. 2 and showing the mounting and terminal portion of an electric heater with the main body of the sheathed resistance element cut away;

Fig. 2 is a front elevation of the mounting and terminal construction shown in Fig. 1;

Fig. 3 is a section taken along the line III-III of Fig. 2;

Fig. 4 is a perspective view showing the inner side of the electrically insulating block that abuts the clamping plate in the assembly shown in Figs. 1 through 3; and

Fig. 5 is a perspective view showing the outer side of the same insulating block and the insulating plug that is received in a passage in the block.

The sheathed heater 11 comprises a helically coiled electrical resistant element positioned in a corrosion resistant tubular metal sheath 13 and insulated therefrom by an insulating material such as magnesium oxide. The heater is bent in the shape of a hairpin or any other desired shape with the end portions of the heater extending generally parallel and adjacent to each other. Terminal pins are electrically connected to the resistance element and extend from within each end of the sheath and are electrically insulated therefrom.

The sheathed end portions of the heater 11 extend through a corrosion resistant copper sheet 20. The sheath 13 is bonded and hermetically sealed in the sheet preferably by brazing. A heavy steel clamping plate 22 having a central opening 23 therein abuts the sheet 20. Abutting the side of the plate 22 opposite the sheet 20 is a ceramic insulating block 24 having a recess 25 aligned with the opening 23 in the plate. The plate opening 23 and the recess 25 in the block define a cavity into Which the terminal portions of the heater extend and within which the heater sheath 13 terminates. The heater terminals extend to the outside of the block for making electrical connections thereto.

The cavity 23-25 is accessible by means of a passage 26 in the block through which molten sealing material 28 may be poured to form an insulating hermetic seal between the sheath 13 and the terminal pins 15. After the material 28 sets or hardens it firmly supports the clamping plate 22 and insulating block 24 relative the sheet 20 and the sheath 13. The electrically insulating sealing material 28 is preferably of the type which will set quickly and which does not require a curing operation. A highly refined asphalt material designed for high temperature use is one of many such suitable materials.

The clamping plate 22 has a flat surface that abuts and is coextensive with the sheet 20, except at the center opening 23 that accommodates the end portions of the heater 11. The wall of the opening in the plate 22 is spaced from the sheath 13 to permit the sealing material 28 to readily flow completely around the end portions of the sheath 13 that extend through the sheet 20. A lip 29 is formed on the block 24 around the edge of the recess and extends into the opening in the plate 22 with a snug fit. This lip is provided primarily to reduce the leakage of the molten sealing material between the block 24 and the plate 22, but it also assists in positioning the plate relative the block during assembly. This invention may be practiced without using the lip, however, since the sealing material when set will hold the clamping plate in fixed position.

The electrical heater terminals comprise terminal strips 30 attached to the terminal pins 15. The terminal strips extend along opposite sides of the central pasasge 26 in the insulating block 24 and are bent to lie in a channel 31 along the outer surface of the block. An insulating plug 32 closes the passage 26 and provides mechanical support for the portions of the terminal strips 30 within the passage and maintains the terminals in spaced relationship. Opposite walls of the passage 26 in the block have grooves 34 to receive the terminal pins. The terminal strips 30 are spot welded to the terminal pins 15 on the sides of the latter opposite the recesses so that the strips 30 provide flat surfaces to be engaged by the plug 32.

The terminal strips 30 are straight when attached to the pins 15 and extend generally parallel to the latter. During assembly the clamping plate 22 and insulating terminal block 24 are positioned on the heater by slipping them over the terminal strips 30 and the latter are thereafter bent to the position shown in Fig. 1 to hold the block and plate in fixed positions. The assembly is then heated to drive off moisture and the cavity is filled by pouring the molten insulating material 28 through the pasasge 26. While the insulating material 28 is still soft the plug 32 is inserted and compresses the material to force it into the ultimate confines of the cavity.

A heater made in accordance with this invention will maintain a very good hermetic seal between the termialso be very strong mechanically. The heater terminals are firmly supported and any normal stresses thereon will not detrimentally affect the hermetic seal.

While the invention has been shown in but one form, it will be obvious tothose skilled in the art that it is not so. limited, but is susceptible of various changes and modifications without departing from the, spirit thereof.

What is claimed is;

1. An immersion heater for mounting in the wall of a liquid containing. receptacle comprising a sheath having an electrical resistance element therein, said sheath having adjacent, generally parallel end portions, a corrosion resistant sheet, said end portions extending through said sheet with a fluid-tight seal therebetween, a clamping plate having a central opening and a flat surface abutting said sheet, an insulating block abutting said plate and having a recess therein aligned with the opening in said plate, said recess andcentral'opening defining a cavity within which the ends of 'said sheath terminate, said block having a passage therethrough providing access to said cavity, an electrical terminal connected to said element and extending fromwithin each end of said sheath, through said passageand exteriorly of said block, and a settable electrically insulating sealing material disposed in'saidcavity, said material being in a set condition and providing a hermetic seal between said terminals and said sheath, said passage being of sutficient size to readily permit'pouring of saidinsulating material into the cavity prior to the setting of the material.

' 2'. An immersion heater for mounting in the wall of a liquid containing receptacle, comprising a sheath having an electricalresistance element therein, said sheath having adjacent, generally parallel end portions, a corrosion resistant sheet, said end portions extending through said sheet with a fluid-tight seal therebetween, a clamping plate having a central'opening and a flat surface abutting said sheet, an insulating block abutting said plate and having a recess therein aligned with the opening in said.

plate, said recess and central opening defining a cavity within which the ends of said sheath terminate, said block'having apassage therethrough for pouring a settable. sealing material into said cavity, an electrical termi-,

rial connected to said element and extending from within each end of said sheath, through, said passage and exter iorly of saidblock, electrically insulating; sealing material in said cavity providing a; hermetic seal between said terminals and said sheath and a plug positioned in said passage to close the latter and mechanically support said terminals relative said block.

3. A heater for mounting in the wall of a liquid con taining receptacle comprising a sheath having an electri-v cal resistance element therein, said sheath having adjacent, generally parallel end portions, an electrical terminal connected to said element and extending from Within each end of the heater sheath, a corrosion resistant sheet fastened to said sheath in fluid-tight relationship adjacent said end portions, a clamping plate abutting said sheet and having a central opening, an insulating block abutting said plate and having a recess therein aligned with said central opening, a lip on said block around the edge of said recess extending intolsaid opening with a snug fit, said recess and central opening defining a cavity within which the ends-of said sheath terminate, said block having a passage therein providing access to said cavity, and electrically insulating sealingmaterial in said cavity providing a seal between said terminals and said sheath, said passage being of suflicient size to permit pouring of said insulating material while in a liquid state into said cavity, said terminals extending through said passage and exteriorly of said block.

4. A sheathed heater for mounting in the wall of a liquid containing receptacle comprising a sheath having an electrical resistance element therein, said sheath having adjacent, generally parallel end portions, an electrical terminal pin connected to said element and extending from within each end of the heater sheath, a corrosion resistant sheet fastened to said sheath in fluid-tight relationship adjacent said end portions, a clamping plate abutting said sheet and having a central opening, an insulating block abutting said plate and having a recess therein aligned with said central opening, a lip on said block around the edge of said recess extending into said opening with a snug fit, said recess and central opening defining a cavity within which the ends of said sheath terminate, said block having a pasasge therein providing access to said cavity, a settable electrically insulating sealing material in said cavity providing a hermetic seal between said terminal pins and said sheath, said passage being of sufiicient size to permit pouring of said insulating material while in a pour-able condition into said cavity, a terminal strip for each of said terminal pins attached thereto and extending along opposite sides of said passage, said strips extending exteriorly of said block and being bent outwardly from said passage to lie along the outer surface of said block, and a plug positioned in said passage between said terminal strips to close said cavity and to provide mechanical support for said terminals.

References Cited in the file of this patent UNITED STATES PATENTS Fox Julyv 20, 1954 

